Arnold Joost van Keppel, 1st Earl of AlbemarleKG, and lord of De Voorst in Guelders (Gelderland) (baptized 30 January 1670, Zutphen – 30 May 1718), was the son of Oswald van Keppel and his wife Anna Geertruid van Lintelo. De Voorst is a large country house near Zutphen, financed by William III, and not unlike the royal palace Het Loo in Apeldoorn.

Arnold Joost van Keppel was born in the Dutch Republic about 1670 and was the heir of a junior branch of an ancient and noble family in Gelderland, and 12th in descent from Walter van Keppel, living in 1179. He achieved fame and wealth as the right-hand man of William III of Orange. He became page of honor to William III in his mid-teens, possibly as early as 1685. Some have claimed that he was William's lover; however despite numerous attempts, no evidence has been found in support of these allegations. Keppel accompanied William to England in the Glorious Revolution of 1688.

While some have asserted that his possible affair with the Prince began when he was only 16, others assert that it was not till later in his life, possibly at the time of a hunting accident when he is said to have drawn the king's attention for his uncomplaining demeanor upon breaking his leg. Public commentary on the king's relationship with him intensified in 1692 when he began to receive grants of land from the king. He became Groom of the Bedchamber and Master of the Robes in 1695. In 1696, he was created the Viscount Bury in Lancashire, and the Baron Ashford of Ashford, Kent. On 10 February 1697, William made Van Keppel the Earl of Albemarle. In 1699, he was awarded the command of the First Life Guards,.

In 1700, William gave Albemarle extensive lands in Ireland, but Parliament obliged the king to cancel this grant. William instead granted him £50,000. The same year he was created a Knight of the Garter. He served both with the English and Dutch troops, was major-general in 1697, colonel of several regiments and governor of 's-Hertogenbosch.

Handsome and engaging, he rivalled Portland (whose jealousy he aroused in the royal favour), possessed William's full confidence, and accompanied him everywhere. In February 1702 William, then prostrated with his last illness, sent Albemarle to the Netherlands to arrange the coming campaign, and he only returned in time to receive William's last commissions on his deathbed, including being entrusted with the king's private papers.

After the death of William III, who bequeathed to him ƒ200,000 and the lordship of Brevost, Albemarle returned to the Netherlands, took his seat as a noble in the States-General, and became a general of cavalry in the Dutch army. He joined the forces of the allies in 1703 in the War of Spanish Succession, was present at the Battle of Ramillies in 1706, and at Oudenaarde in 1708, and distinguished himself at the siege of Lille. He commanded at the siege of Aire in 1710, led Marlborough's second line in 1711, and was general of the Dutch forces in 1712, being defeated at Denain after the withdrawal of Ormonde and the English forces and taken prisoner. He died on 30 May 1718, at the age of forty-eight.

Albemarle married Geertruid Johanna Quirina, daughter of Adam van der Duyn, by whom he had :